This invention relates to a brake booster-mounting construction, and more particularly to a brake booster-mounting construction suited for mounting an automobile brake booster on a vehicle.
A brake booster converts a pressing-down force of a brake pedal into a boosting force, utilizing an intake negative pressure, and transmits it to a master cylinder. In such a brake booster, one wall portion of a shell is fixedly secured to a vehicle body, and a master cylinder block is mounted on other wall portion of the shell. In this conventional mounting construction, stud bolts are formed on and protruded from a rear shell (which is adapted to face the vehicle body) and a front shell (which is adapted to face the master cylinder), and these stud bolts are passed respectively into the vehicle body and the master cylinder and are fastened thereto by nuts.
In the above conventional brake booster, the shell is formed by pressing a thin steel sheet into a required shape in order to achieve a lightweight construction. When a heavy part, such as an anti-lock brake system provided integrally with the master cylinder, is incorporated in the shell, a problem of durability due to vibrations has arisen. More specifically, in the brake booster, usually, the rear shell is fixedly secured to the vehicle body, and the front shell is fixedly connected to the master cylinder. In such a mounting construction, when vibrations of the vehicle act on the heavy part, the vibrations concentrate on the portion of connection between the rear shell (which is fixedly connected to the vehicle) and the stud bolts. Therefore, it is necessary to increase a vibration-resistant strength particularly at the rear shell side so as to provide a sufficient reinforcement. In view of this, Japanese Laid-Open (Kokai) Patent Application No. 71472/88 proposes a construction of the type in which a rear shell side is fastened to a vehicle body via a reinforcement member provided within a minor diameter portion. With this brake booster-mounting construction, however, vibrations can not still be suppressed, and the rattling due to the loosening of stud bolts can not be reduced.